This application claims the priority of the commonly owned copending German patent application Serial No. 101 23 729.4 filed May 15, 2001. The disclosure of the just mentioned German patent application, as well as that of each US and foreign patent and patent application identified in the specification of the present application, is incorporated herein by reference.
This invention relates to improvements in hydrodynamic or hydrokinetic torque converters, for example, to torque converters which can be utilized in the power trains of motor vehicles.
A hydrodynamic torque converter which is utilized in the power train of a motor vehicle is installed between the rotary driving or output element or component of the prime mover (e.g., between the crankshaft or camshaft of an internal combustion engine or between the output element of a hybrid prime mover) and a rotary driven or input element or component, e.g., the input shaft of the change-speed transmission which can drive or which can be driven by one or more road-contacting wheels (for example, by way of a differential). The output element of the prime mover drives the rotary housing and the converter pump assembly (hereinafter called pump) of the torque converter, and the pump can drive the input shaft of the transmission.
A so-called bypass or lockup clutch (hereinafter called lockup clutch) is provided in many types of hydrodynamic torque converters to transmit torque directly between the output element of the engine (such as from the housing of the torque converter) and the input shaft of the transmission by way of at least one friction disc, such as a clutch disc. As a rule the housing further accommodates a stator which is installed between the pump and the turbine and can serve to improve the circulation of hydraulic fluid (such as oil) in the interior of the torque converter.
The lockup clutch employs a piston which shares the angular movements of the output element of the prime mover (i.e., of the housing and the pump of the hydraulic torque converter) and must be moved axially to engage (close) or disengage (open) the clutch. The means for moving the piston comprises two compartments or chambers (hereinafter called chambers) which flank the piston. One of the chambers is disposed between the piston and the housing (e.g., a wall which is or which can be resilient and is non-rotatably affixed to the output element of the prime mover), and the other chamber is disposed between the piston and the turbine of the torque converter.
When the torque converter in the power train of a motor vehicle is in actual use, it can develop dynamic pressures during engagement (closing) of the lockup clutch. The development of such dynamic pressures is attributable to the differences between the RPM of the piston of the lockup clutch and the RPM of the turbine of the torque converter; these stresses are highly undesirable because they oppose or are apt to oppose the optimal (most satisfactory) engagement (closing) of the lockup clutch.
An object of the present invention is to provide a hydrodynamic torque converter the operation of which during engagement and/or during disengagement of its lockup clutch (including the operation with slip) is more predictable and more satisfactory than that of conventional hydrodynamic torque converters.
Another object of our present invention is to provide a novel and improved hydrodynamic torque converter of the type embodying a lockup clutch.
A further object of the instant invention is to provide a novel and improved lockup clutch for use in hydrodynamic torque converters.
An additional object of the invention is to provide a novel and improved turbine for use in hydrodynamic torque converters, especially in torque converters which are installed in the power trains of automobiles or other types of motor vehcles.
Still another object of this invention is to provide a novel and improved method of controlling dynamic pressures during disengagement of the lockup clutch in a hydrodynamic torque converter.
A further object of the present invention is to provide a novel and improved method of and a novel and improved arrangement for controlling or regulating the flow of hydraulic fluid between as well as into and from the chambers which flank the axially movable piston of the lockup clutch in a hydrodynamic torque converter.
Another object of our invention is to provide a hydrodynamic torque converter wherein the pressure of fluid in the chamber between the piston of the lockup clutch and the turbine of the torque converter can be regulated (such as increased) with a much higher degree of predictability than in heretofore known torque converters.
A further object of the invention is to provide a hydrodynamic torque converter at least some component parts of which can be cooled more effectively and more predictably than in conventional hydrodynamic torque converters.
An additional object of this invention is to provide a novel and improved method of regulating the flow of hydraulic flid into one of the chambers of the torque converter during disengagement and/or in the disengaged condition of the lockup clutch, especially of regulating the flow of hydraulic fluid into the chamber between the piston of the lockup clutch and the turbine of the torque converter.
Still another object of the present invention is to provide a method of the above outlined character the practice of which does not necessitate resort to numerous, bulky, complex and/or expensive component parts in addition to or in lieu of those employed in conventional torque converters employing lockup clutches.
A further object of the instant invention is provide a power train, particularly for use in motor vehicles, which employs the above outlined torque converter.
One feature of the present invention resides in the provision of a hydrodynamic converter for transmission of torque between rotary driving and driven components. The improved torque converter comprises a rotary housing including a pump and serving to receive torque from the driving component, a rotary turbine which is disposed in the housing and is arranged to receive torque from the pump for transmission of torque to the driven component, and a lockup clutch which is provided in the housing and includes a piston rotatable with the driving component and defining a first chamber with the housing and a second chamber with the turbine. The clutch is disengageable in response to admission of a hydraulic fluid into the first chamber to move the piston toward the turbine, and the clutch is disengageable in response to admission of hydraulic fluid into the second chamber along a first path to move the piston toward the housing. The improved torque converter further comprises means for admitting into the second chamber a pressurized hydraulic fluid along at least one second path, and means for at least partially sealing the second path in the disengaged condition of the lockup clutch.
At least a portion of the second path can be defined by the turbine.
The turbine and the driven component are rotatable about a common axis, and the turbine can include a portion which extends at least substantially radially of and away from the common axis; the at least one second path can be provided in such portion of the turbine. The just mentioned portion of the turbine can include a collar and at least a portion of the at least one second path can be defined by at least one passage in the collar. Such passage can include a hole or bore which is at least substantially and/or at least partially parallel to the common axis.
The turbine can further include a hub which surrounds the driven component, and the aforementioned collar can surround the hub. The at least one second path can be provided in the collar adjacent the hub. The sealing means can comprise a closure for the at least one second path; such closure can surround the hub between the piston and the collar and can be arranged to at least partially seal the at least one second path in response to engagement of the lockup clutch. The closure can include or constitute an annular member which is movable axially of the hub between the piston and the collar.
The driving component can include a rotary disc-shaped member which is of one piece with or is affixed to the housing, and the driven component can include a rotary shaft, e.g., the input shaft of the change-speed transmission in the power train of the motor vehicle.
The torque converter can further comprise a torsional vibration damper which operates between the piston and the driven component, and a stator which is provided in the housing intermediate the pump and the turbine.
The turbine and the housing are or can be rotatable about a common axis, and one of the two chambers can be nearer to the common axis than the other chamber.
The piston and the housing can define a passage for the flow of fluid from the first chamber into the second chamber in the disengaged condition of the lockup clutch. Furthermore, the piston and the housing can define a passage for the flow of hydraulic fluid from the second chamber into the first chamber in the engaged condition of the lockup clutch.
The piston can be provided with friction linings which are engageable with the housing and/or with another rotary part of the torque converter at least in the engaged condition of the lockup clutch.
Another feature of the present invention resides in the provision of a method of operating a hydrodynamic torque converter which is or which can be provided in the power train of a motor vehicle and includes a rotary housing having a pump and being arranged to receive torque from a driving component of the prime mover in the power train, a rotary turbine disposed in the housing and arranged to receive torque from the pump for transmission of torque to a driven component of the power train, and a lockup clutch provided in the housing and having a piston rotatable with the driving component and movable in the housing toward and away from the turbine intermediate first and second chambers to disengage the clutch in response to admission, of pressurized hydraulic fluid into one of the chambers and to engage the clutch in response to admission of pressurized hydraulic fluid into the other chamber. The improved method comprises the steps of admitting into the one chamber a hydraulic fluid at a pressure higher than the pressure then prevailing in the other chamber to thus move the piston toward the turbine with attendant reduction of the volume of the other chamber, introducing into the other chamber a hydraulic fluid at a pressure higher than the pressure then prevailing in the one chamber to thus move the piston away from the turbine and to reduce the volume of the one chamber, and simultaneously conveying into the other chamber a hydraulic fluid through at least one passage provided in the turbine and communicating with the other chamber only in the course of the introducing step.
At least one of the aforementioned steps can include conveying hydraulic fluid through and/or along the driven component.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved torque converter itself, however, both as to its construction and the modes of assembling, installing and operating the same, together with numerous additional important features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.